SDSS-III was able to measure the expansion rate of the distant universe by using quasars to probe the distribution of hydrogen along the line of sight from the each quasar (red dots in the upper left) to the 2.5-meter Sloan Foundation Telescope on Earth (abstractly represented as the plane in the lower right). // Illustration by Z. Rostomian (LBNL)/N. Ross & BOSS Lyman-alpha team (LBNL)/Springel, et al./Virgo Consortium/Max Planck Institute for Astrophysics